The origins of the Greenwich observatory

Abstract

Although the foundation of England's national observatory may be regarded as an inevitable consequence of progressive trends in seventeenth-century astronomy, cartography, and navigation, it was the chance conjunction of two related events which caused it to be established exactly 300 years ago. One was the attempt in 1674 of the Sieur de St. Pierre, a Frenchman at the Court of Charles II, to interest that king in a proposal for a lunar method of finding longitude at sea. The other was the condemnation of the practicability of his method by John Flamsteed on the same ground — the inadequacy of the necessary observational data — that had led a French scientific commission to reject methods of a similar nature put forward by Jean Morin some 40 years earlier. A reconstruction of the method ascribed by Flamsteed to St. Pierre serves to confirm St. Pierre's accusation that Flamsteed supplied him with calculations rather than observations by which to demonstrate his method, appears to be justified inasmuch as Flamsteed converted two of his own Derby observations of the Moon's altitude to corresponding values on arbitrary meridians close to those of Brunswick and Danzig respectively, before presenting these data to the Frenchman as if they had been directly observed at those places. Significantly, the method already being applied by Flamsteed 2 years previously when determining errors in the Moon's celestial position from micrometric measurements of small angular distances from certain bright zodiacal stars for the two dates in question, is the very same as that which he ascribed to St. Pierre.